The word "exist" is problematic, because the three kinds of things you mention are three different kinds of things. Even if one were to say they all "exist", they don't all exist in the same way.

Can you give some more context about why this question concerns you? We could give a better answer if we knew more about why you want to know.

For example, we know that time and matter are inseparable. If time exists, then matter exists, and vice versa. I'm specifically wondering if it is possible for energy to exist without time. Could an entire universe be made of nothing but energy while being outside time?

If you take a close look at international standards, The fundamental unit of energy is the Joule, which is expressed in terms of meters, kilograms and seconds. Since the second and kilogram are fundamental to the internationally recognized unit of energy, it follows there is no internationally accepted definition of energy independent of time or matter. You will notice that distance [meters] is also a component in the fundamental definition of energy, so we may as well lump that in there, as well.

We know time and matter are inseparable because all of our values for time are defined with respect to matter. What is a day? One full rotation of the earth. What is a year? One full revolution around the sun. What is one second? “‘9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom.’”[1] In any and all cases one can name, time is defined with respect to matter. If there was no matter, then time would not exist. Likewise, if time did not exist, then there would be no matter. What I was wondering is if energy could exist without matter. However, Chronos made the excellent point that energy is defined with respect to matter as well, so that answers my question.

If you take a close look at international standards, The fundamental unit of energy is the Joule, which is expressed in terms of meters, kilograms and seconds. Since the second and kilogram are fundamental to the internationally recognized unit of energy, it follows there is no internationally accepted definition of energy independent of time or matter. You will notice that distance [meters] is also a component in the fundamental definition of energy, so we may as well lump that in there, as well.

Thank you Chronos! That is an excellent point and answers my question.

Light has an energy content. It also has an intrinsic spin angular momentum for a photon, and linear momentum. While it MAY be converted into entities with mass via a set of processes that obeys conservation laws, light itself has no mass content.

Secondly, another simple example is the electrostatic energy, such as the electrostatic potential energy. It depends only on charge content. Now, granted that a "charge" usually is carried by entities with mass (we are ignoring the exotic effects in many-body interactions, such as that resulting in spin-charge separation). Still, it doesn't change the fact that the calculation and definition of such electrostatic energy depends only on charge and not on the mass of these entities.

So I consider these two as examples where energy is not intrinsically tied to mass. Energy is intrinsically tied to space and time.

That just means we, here on Earth, use matter to measure time. It doesn't justify the claim that "time and matter are inseparable" period.

If the universe had no matter/energy in it, then time would not be ticking. Nothing would be happening, and there would be no way to differentiate units of time. One second and one million years would be essentially equivalent, so time would be both meaningless and nonexistent. If there is matter in the universe, then we may speak of time as existing. If there is no matter, then there is no time, and conversely, if time cannot be measured anywhere in the universe, then there must be no matter anywhere in the universe (or else the entire universe is frozen still and stuck that way for eternity).

Sorry. I put it here by mistake. My bad.
I asked a different question in the Cosmology Forum that was about Cosmology, but it got deleted for apparently not following the forum rules (which is ridiculous because I did follow the rules). Ironically, this question (which is not directly about Cosmology) was not deleted.

Light has an energy content. It also has an intrinsic spin angular momentum for a photon, and linear momentum. While it MAY be converted into entities with mass via a set of processes that obeys conservation laws, light itself has no mass content.

Secondly, another simple example is the electrostatic energy, such as the electrostatic potential energy. It depends only on charge content. Now, granted that a "charge" usually is carried by entities with mass (we are ignoring the exotic effects in many-body interactions, such as that resulting in spin-charge separation). Still, it doesn't change the fact that the calculation and definition of such electrostatic energy depends only on charge and not on the mass of these entities.

So I consider these two as examples where energy is not intrinsically tied to mass. Energy is intrinsically tied to space and time.

BTW, I do not understand why this is in the Cosmology forum.

Zz.

Thank you for those useful examples. I'll look into those. Thanks again!

If the universe had no matter/energy in it, then time would not be ticking. Nothing would be happening, and there would be no way to differentiate units of time. One second and one million years would be essentially equivalent, so time would be both meaningless and nonexistent. If there is matter in the universe, then we may speak of time as existing. If there is no matter, then there is no time, and conversely, if time cannot be measured anywhere in the universe, then there must be no matter anywhere in the universe (or else the entire universe is frozen still and stuck that way for eternity).

Then you might want to contact whoever actually understood the Big Bang model of the universe and wrote this at the CERN webpage:

In the first moments after the Big Bang, the universe was extremely hot and dense. As the universe cooled, conditions became just right to give rise to the building blocks of matter – the quarks and electrons of which we are all made. A few millionths of a second later, quarks aggregated to produce protons and neutrons.

This implies that for a very short time, there was ZERO matter in the universe before the first leptons and quarks formed. According to you, the universe could not have existed because there is no "time".

Staff: Mentor

If the universe had no matter/energy in it, then time would not be ticking. Nothing would be happening, and there would be no way to differentiate units of time.

I realize this sounds plausible, but it is not correct according to our current theories. According to General Relativity, it is perfectly possible to have a spacetime with no matter and energy in it that still has a definite notion of time.

Then you might want to contact whoever actually understood the Big Bang model of the universe and wrote this at the CERN webpage:

This implies that for a very short time, there was ZERO matter in the universe before the first leptons and quarks formed. According to you, the universe could not have existed before there is no "time".

Zz.

Thanks. You are being very helpful. This is actually what I was trying to ask about with my initial question.